On Fri, Nov 26, 2021 at 10:33 AM AKASHI Takahiro takahiro.akashi@linaro.org wrote:
On Fri, Nov 26, 2021 at 10:28:19AM +0100, Arnd Bergmann wrote:
One problem I've had with network benchmark was reaching the link limit. On an recent Arm server the bottleneck was 10GbE so I was unable to compare different software optimizations (measuring mainly bandwidth, though, not latency). If that happens and you do need a physical link (e.g. testing VFIO or HW acceleration) then 50/100+ GbE will be needed, and that's a different budget. Currently I do VM <-> host userspace for network benchmarks so everything is CPU-bound.
I would think that latency testing is more useful than throughput testing then. I'd focus on the maximum latency in a bufferbloat scenario here, flooding the link with large packets while measuring the round-trip ping time.
While 'latency' can mean different things, is the round-trip time what we want to know?
For instance, jitters among (one-way) packets may be more important.
Round-trip latency is what you can actually measure easily, and if everything goes well, it will be consistently low. If you see unexpected latency here, you can then spend additional effort to find out which side introduced it.
Arnd